A piezoelectric motor is a next-generation motor using the piezoelectric effect of a piezoelectric ceramic which vibrates according to variation in an electric field applied thereto. The piezoelectric motor denotes a noiseless motor having an ultrasonic driving frequency above 20 KHz, which is beyond the range of human hearing, and is also called an ultrasonic motor. Compared to a typical electromagnetic motor, a piezoelectric motor has a generation force of 3 kg cm or less, a response speed of 0.1 ms or less, a size that one tenth the size of a typical electromagnetic motor or smaller, and a precision of 0.1 m or smaller. Accordingly, the piezoelectric motor has been widely used in application fields requiring high level torques and low speeds, such as the implementation of the zoom function, auto-focusing function, and shake reduction function of digital cameras, or the driving of a pickup lens in a Compact Disc (CD)/Digital Versatile Disc (DVD)-Read Only Memory (ROM) drive.
Generally, a piezoelectric motor can be implemented using a vibration propagation method, such as a flexural wave type or standing wave type, but this vibration propagation method is disadvantageous in that it is difficult to obtain a given desired amplitude due to the abrasion of a contact portion when the piezoelectric motor is continuously driven.
Korean Patent Registration No. 10-0443638 (the prior art) was proposed as an alternative measure for overcoming this disadvantage, and relates to a piezoelectric linear motor, which linearly moves a movable element mounted on a movable shaft by utilizing a bending motion performed through an elastic body and a piezoelectric plate as a driving source.
The piezoelectric linear motor disclosed in the prior art is advantageous in that it has a small size and a relatively simple manufacturing process and provides a fast operating speed, compared to conventional motors, but is problematic in that, since the piezoelectric ceramic is formed in a disk shape, a separate elastic plate must be joined thereto to obtain displacement, so that the manufacturing cost thereof increases, and the manufacturing process thereof is complicated. Further, according to the prior art, the movement displacements of the movable shaft and movable element are limited to certain magnitudes, thus limiting the range of products to which the motor can be applied in proportion to the limited magnitudes.